The present disclosure relates generally to the chemical processing of wood pulps. More specifically, the present disclosure relates to the use of separation aids in black liquor recovery processes.
The alkaline pulping of wood during the Kraft process yields wood pulp in addition to various recoverable naval stores including turpentines and tall oil soap. Recovery of tall oil soap from the spent pulping liquor is an important unit operation in the pulping process because the tall oil soap is a sellable feedstock that is further processed and fractionated into tall oil fatty acids, resin acids and phytosterols.
Tall oil fatty acids are useful in a myriad of chemical applications as a fatty acid source and upon further derivatization yields surfactants, alkyd resins and polyamide resins useful in numerous applications including cosmetics, printing inks and surface coatings. Importantly, phytosterols are a natural source of various precursor steroidal compounds (e.g. β-sitosterol) useful in pharmaceutical applications including the treatment of cardiovascular disease and its underlying conditions, lipid metabolism and cancers.
In addition to value as a chemical feedstock, the tall oil soap, if not managed properly can cause operational issues within the Kraft recovery process and subsequent papermaking processes. Some these operational issues may include evaporator fouling, evaporator scaling, pitch formation, bleach chemical demand, paper machine foaming, recovery furnace blackouts, wastewater treatment plant performance and rosin acid soaps accounting for 80% of plant effluent toxicity.